East and west oriented walls: a critical approach to comfort

Abstract

The primary aim of this paper is to compare the thermal and energetic response under periodic conditions of two west-oriented wall systems, which have the same performance when analyzed under steady-state environments. Thermal inertia has been addressed using periodic solutions of the heat conduction equation proposed by Fourier, by means of harmonic analysis, for a period of twenty-four hours, in the region of Campinas - SP. In Brazil, walls and roof systems have traditionally been designed using the steady-state overall heat transfer coefficient (U-value). Uvalues only allow preliminary design decisions for some wall and roof systems, as they do not encompass the dynamic performance of the thermal wave. The results show that two identical walls under steady-state conditions may have very distinct thermal and energetic performances, when analyzed under dynamic environments. The suggested inferences are that the selection of local walls and roof systems should be based on their ability for peak load leveling and on the consequences for cooling energy demand, and that the use pattern of the building has also to be considered.